Liquid infusion apparatus for radiofrequency tissue ablation

ABSTRACT

An apparatus for delivering electrical energy includes a cannula and one or more needles extendable from and retractable into a lumen of the cannula. A distal portion of each needle is extendable from the lumen and terminates in a tissue-piercing distal tip. Each distal portion is formed from an electrically conductive and porous material, thereby providing a porous electrode through which electrolytic fluid may flow for delivering electrical energy to tissue surrounding the distal portion. The cannula is introduced into a tissue structure of a patient, the one or more needles are advanced from the cannula, saline is introduced from the porous material to surrounding tissue, and electrical energy from an RF generator is delivered to ablate tissue within the tissue structure.

FIELD OF INVENTION

The present invention relates generally to apparatus for infusing fluidsinto tissue, such as a tumor, to enhance thermal heating and ablation ofthe tissue using radio frequency electrical energy.

BACKGROUND

Electrosurgical instruments for delivering radio frequency (RF)electrical energy into solid tissue are known. For example, publishedPCT application WO 96/29946 discloses electrosurgical probes thatinclude a number of independent wire electrodes that may be extendedinto tissue from the distal end of a cannula. The electrodes may beenergized in a monopolar or bipolar manner to heat and necrose a targettissue region. Such probes have been suggested for treating tumorswithin organs, such as the liver, kidney, pancreas, stomach, and spleen.

To enhance heating and necrosis, saline may be injected into the targetregion before delivering electrical energy. Generally, this involvesadvancing a needle from a syringe into the tissue before or afteradvancing the electrodes from an electrosurgical probe into the targetregion. Saline may be delivered from the syringe into the tissue throughthe needle, and then the electrodes may be energized to deliver RFenergy and necrose tissue within the target region. Alternatively,saline may be delivered through a lumen in one or more of the wireelectrodes. Saline may increase heating of the tissue, therebyincreasing the size of the resulting lesion, as compared to energizingthe electrodes without saline.

Because of inhomogeneities in the tissue of the target region, however,the saline injected by the syringe may not be perfused into the targetregion in a desired manner. For example, the saline may be perfused intotissue away from the electrodes, or only locally within a portion of thetarget region. Thus, the tissue within the target region may not beuniformly heated and necrosed as desired, possible requiring multipletreatments to ensure that the target region is successfully necrosed. Inaddition, where a separate syringe is used to deliver the saline, thesyringe and probe require separate approaches into the tissue,complicating access and creating multiple tracks through the interveningtissue that may need to be closed and allowed to heal.

SUMMARY OF THE INVENTION

In accordance with one aspect of the invention, an apparatus is providedfor delivering electrical energy to tissue within a patient, theapparatus including a tubular member having a proximal end, a distal endsized for insertion into a body of a patient and a lumen extending fromthe distal end towards the proximal end. In one embodiment, the tubularmember may be a substantially rigid cannula having a sharpened distaltip for advancing the cannula through tissue.

One or more needles are extendable from the lumen beyond the distal endof the tubular member, each needle having a distal tip for penetratingtissue. At least one (and preferably all) of the one or more needles hasan infusion lumen for delivering fluid to an outlet in its distal tip.In addition or alternatively, at least a distal portion of the needle(s)may be formed from a porous material, e.g., a sintered stainless steel.A source of conductive fluid, e.g., saline, are connected to theinfusion lumen and/or porous material of the respective needle(s) fordelivering the fluid to tissue beyond the distal tip(s) thereof.

In embodiments of the invention, the needle(s) are electrodes fordelivering electrical energy to tissue adjacent the distal tip. Forexample, a distal portion of the needle(s) may include a conductiveregion defining an electrode. Preferably, the needle(s) are formed fromelectrically conductive material such that an exposed portion of eachneedle forms an electrode. A source of electrical energy, e.g., an RFgenerator, is coupled to the one or more needles in a monopolar orbipolar configuration, for delivering electrical energy to tissuesurrounding the needle(s) when deployed in a patient.

The needle(s) are preferably movable from a retracted configurationwithin the lumen of the tubular member to an extended configuration,wherein distal portion(s) of the needle(s) extend beyond the distal endof the tubular member. In a preferred embodiment, a plurality of theneedles are provided having distal tips that extend at different axialand radial distances from one another in the extended configuration,thereby defining a spherical or other three-dimensional shape in theexpanded configuration.

In accordance with another aspect of the present invention, an apparatusis provided for delivering electrical energy to tissue within a patientthat includes a tubular member having a proximal end, a distal end sizedfor insertion into a body of a patient, and a lumen extending betweenthe proximal and distal ends. A plurality of opposing members areextendable from the distal end of the tubular member, the opposingmembers being extendable away from one another and directable towardsone another for engaging tissue between inner surfaces of the opposingmembers.

The opposing members include one or more electrodes for deliveringelectrical energy to tissue engaged between the opposing members. One ormore hollow needles extend from an inner surface of at least one, andpreferably each, of the opposing members. Each needle may include asharpened tip for penetrating tissue engaged between the opposingmembers and an outlet in the sharpened tip communicating with a lumen inthe opposing member for delivering conductive fluid from the lumen intotissue penetrated by the sharpened tip. A source of electrical energymay be coupled to the electrodes for delivering electrical energy toablate tissue engaged between the opposing members.

In one embodiment, the opposing members may extend from a control memberextending through the lumen of the tubular member. The opposing membersmay be directable towards one another by directing the control memberproximally to at least partially withdraw the opposing members into thelumen. In addition, the control member may include an infusion lumencommunicating with the outlets of the needles. A source of conductivefluid may communicate with the infusion lumen for delivering conductivefluid to the outlets of the needles.

Other objects and features of the invention will become apparent fromconsideration of the following description taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings illustrate the design and utility of preferred embodimentsof the invention, in which similar elements are referred to by commonreference numerals, and in which:

FIG. 1 is a side view of a first preferred embodiment of an apparatusfor ablating tissue using electrical energy, including a cannula and anarray of electrodes deployable from the cannula.

FIG. 2 is a detail of the distal end of the cannula shown in FIG. 1,showing the array of electrodes in a collapsed configuration within thecannula.

FIG. 3 is a detail of the distal end of the cannula shown in FIG. 1,showing an alternative array of electrodes deployed from the cannula.

FIG. 4 is a cross-sectional view of a float valve for use with theapparatus of FIG. 1.

FIGS. 5A and 5B are cross-sectional views of a tissue structure, showinga method for treating a tumor within the tissue structure using theapparatus of FIG. 1.

FIGS. 6A-6C are side views of a second preferred embodiment of anapparatus for ablating tissue using electrical energy, including acannula and an opposing pair of jaw-like electrodes deployable from thecannula.

FIGS. 7A-7D are cross-sectional views of a tissue structure, showing amethod for treating a tumor within the tissue structure using theapparatus of FIGS. 6A-6C.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

Turning to the drawings, FIGS. 1-4 show a first preferred embodiment ofan apparatus 10 for treating tissue, such as a benign or malignant tumorwithin a tissue structure (not shown). Generally, the apparatus 10includes a cannula or other introducer 12 and an array of electrodes 14deployable from the cannula 12. In addition, the apparatus 10 mayinclude a source of electrical energy 16 and/or a source of conductivefluid 18 coupled to the array of needles 14.

The cannula 12 is an elongate tubular member including proximal anddistal ends 20, 22 and a lumen 24 therein extending proximally from adistal port 26 towards the proximal end 20, thereby defining alongitudinal axis 21. The lumen 24 may extend to the proximal end 20,although the proximal end 20 may be substantially closed as shown.Alternatively, the lumen 24 may extend to a proximal port (not shown) inthe proximal end 20 for removably receiving instruments, e.g., the arrayof electrodes 14 or a stylet (not shown), therethrough. The cannula 12may also include a handle 25 on the proximal end 20 to facilitatemanipulation of the cannula 12 and/or the array of electrodes 14.

The cannula 12 may be formed from a substantially rigid material, suchas metal or plastic, and/or may be formed from an electricallyinsulating material. The distal end 22 of the cannula 12 may terminatein a sharpened or tissue-penetrating tip, e.g., a beveled tip 28 (notshown, see FIGS. 5A and 5B) to facilitate advancing the cannula 12through tissue. Alternatively, the cannula 12 may be formed from asemi-rigid or flexible material, and a stylet (not shown) may beintroduced into the lumen 24 from a proximal port (not shown). Thestylet may enhance a rigidity of the cannula 12, and/or may include asharpened distal tip (also not shown) that may extend beyond the distalend 22 of the cannula 12 to facilitate advancing the cannula 12 throughtissue.

The array of electrodes 14 includes a plurality of elongate needles 30,each of which includes a proximal end 31 and a sharpened ortissue-penetrating distal tip, e.g., a beveled tip 32. At least one ofthe needles 30, and optionally all of the needles 30, may include aninfusion lumen 34 for delivering a fluid to an outlet 36 in its distaltip 32. Alternatively, the needle(s) 30 may include multiple outlets(not shown) in the distal tip(s) 32, e.g., for delivering fluid in apredetermined pattern beyond the distal tip(s) 32. The needles 30 extendproximally through the lumen 24 of the cannula 12 and the proximal ends31 may be connected to a hub 38, which may include a side port 40communicating with the infusion lumen(s) 34 of the needle(s) 30.

A fluid line 42 may extend from the side port 40 to the source ofconductive fluid 18 for delivering electrically conductive fluid, e.g.,hypertonic saline, into the infusion lumen(s) 34 of the needle(s) 30.The source of conductive fluid 18 may include a manual source ofconductive fluid, such as a syringe (not shown), or may include a pump(not shown) for continuously or intermittently delivering saline duringa procedure. The fluid line 42 may include a relief valve 44, formaintaining the pressure of fluid being delivered via the fluid line 42below a predetermined pressure. For example, the relief valve 44 mayopen at the predetermined pressure to prevent the patient from beingexposed to excessive fluid pressures.

In addition, the fluid line 42 may include a float valve 46, such asthat shown in FIG. 4, for ensuring that only liquids, such as saline,are delivered via the needles 30. For example, the float valve 46 mayinclude a hydrophobic membrane 48 covering, a reservoir 50 through whichgases, such as air, may pass freely. Thus, fluid leaving the reservoir50 may be substantially free from air bubbles that may otherwise causeinjury if released within a patient's body, e.g., into a patient'svasculature.

With particular reference to FIGS. 1 and 2, the array of electrodes 14may be movable from a collapsed configuration, e.g., when retracted intothe lumen 24 of the cannula 12 (see FIG. 2), to an expandedconfiguration, e.g., when extended beyond the distal end 22 of thecannula 12 (see FIG. 1). Preferably, the needles 30 are biased to expandtowards the expanded configuration, but may be resiliently compressedinto the collapsed configuration when withdrawn into the lumen 24 of thecannula 12. In a preferred embodiment, the needles 30 are formed from anelastic or superelastic material, e.g., stainless steel or Nitinol, thatmay be sufficiently strong and biased to expand towards the expandedconfiguration even as the needles 30 are advanced through tissue.

Distal portions 33 of the needles 30 may expand such that the array ofelectrodes 14 defines a generally symmetrical shape, e.g., an umbrellaor everted shape, as shown in FIG. 1. In one embodiment, the array ofelectrodes 14 may generally define a plane, as disclosed in U.S. Pat.Nos. 6,050,992 and 6,212,433. The disclosures of these references andany others cited therein are expressly incorporated herein by reference.Alternatively, as shown in FIG. 3, some of the needles 30′, 30″ may havedifferent lengths than others and/or may have different radii ofcurvature to which they are biased. When fully deployed, as shown, thedistal portions 33′, 33″ of the needles 30′, 33″ may extend differentaxial distances from the distal end 22 of the cannula 12 and/or mayextend different radial distances from the longitudinal axis 21 in theexpanded configuration. Thus, the array of electrodes 14′ may define agenerally spherical or other three-dimensional configuration whenextended into the expanded configuration. This configuration may enhancetreatment of a larger target tissue region, as explained further below.

The distal portion(s) 33 of one (or more) of the needle(s) 30 mayinclude an electrode for delivering electrical energy to tissue adjacentthe distal tip(s) 32. In one embodiment, each of the needles 30 may beformed from an electrically conductive material, such as stainless steelor Nitinol. Thus, the entire exposed distal portions 33 of the needles30 extending beyond the distal end 24 of the cannula 12 may defineelectrodes. In this embodiment, the cannula 12 may be formed from anelectrically insulating material. Alternatively, the needles 30 may beformed from electrically insulating material, e.g., plastic, and mayinclude one or more electrically conductive regions (not shown) on thedistal portions 33 that define electrodes. In this alternative, theneedles 30 may include wires or other conductors (not shown) extendingproximally from the electrodes, e.g., within the needles 30 to theirproximal ends 31.

The needles 30 may be electrically coupled to the source of electricalenergy 16, preferably a radio frequency (RF) generator, for deliveringelectrical energy to the distal portions 33 of the needle(s) 30. The RFgenerator 16 may be coupled to the proximal end 20 of the cannula 12and/or to the hub 38, e.g., by a cable (not shown), which may, in turn,be coupled to the proximal end(s) 31 of the needles 30.

The RF generator 16 may be configured for delivering RF energy in amonopolar or a bipolar mode. In a monopolar mode, all of the needles 30may be coupled to one pole of the RF generator 16. A passive electrode(not shown) may be provided that may be coupled to an opposite pole ofthe RF generator 16. Preferably, the passive electrode is a pad (notshown), e.g., having a relatively large surface area compared to thedistal portions 33 of the needles 30, that may be placed against anouter surface of a patient being treated.

Alternatively, in bipolar mode, some of the needles 30 may be coupled toone pole, while other needles 30 may be coupled to the opposite pole. Inanother alternative, all of the needles 30 may be coupled to one pole,and an electrode (not shown) may be provided on the distal end 24 of thecannula 12 that may be coupled to the opposite pole. In yet a furtheralternative, all of the needles 30 may be coupled to one pole, and aninternal surface electrode (not shown) may be coupled to the oppositepole that may be placed in contact with a surface of the tissuestructure being treated. Such a surface electrode is disclosed in U.S.Pat. No. 6,212,433 incorporated by reference above.

Turning to FIGS. 5A and 5B, the apparatus 10 may be used to treat avariety of soft tissues, e.g., to heat and/or ablate a benign ormalignant tumor. For example, the apparatus 10 may be used to treattumors within organs or other tissue structures, such as a liver,kidney, pancreas, stomach, spleen, prostate, breast, and lung.

Initially, the array of electrodes 14 may be provided within the lumen24 of the cannula 12, i.e., in the collapsed configuration. The distalend 22 of the cannula 12 may be advanced into a target tissue region 92of a patient that is to be treated. For example, a surgical proceduremay be used to expose a tissue structure 94, e.g., a liver or otherorgan, having a tumor or other target region 92 therein. The sharpeneddistal tip 28 of the cannula 12 may be inserted into the tissuestructure 94 until the distal end 22 is disposed within or adjacent tothe target region 92, as shown in FIG. 5A. Alternatively, it may bepossible to insert the cannula 12 directly through the patient's skin,any intervening tissue (not shown), and into the tissue structure 94,without requiring a procedure to expose the tissue structure 94.

The cannula 12 may be manipulated while using external imaging, such asMRI, fluoroscopy, and the like, to place the distal end 24 in apredetermined position relative to the target tissue region 92. Forexample, the distal end 22 of the cannula 12 and/or the needles 30 mayinclude markers, e.g., radiopaque markers, that may facilitateidentifying the location of the cannula 12 using external imaging.

If the cannula 12 is flexible or does not include a sharpened distaltip, the cannula 12 may be advanced through an introducer (not shown)previously placed into the target tissue region 92. Alternatively, astylet (not shown) may be inserted into the proximal end 20 (e.g.,without the array of electrodes 14 in the cannula 12) and advanced untila sharpened distal tip (also not shown) of the stylet extends beyond thedistal end 22 of the cannula 12. The sharpened tip of the stylet maythen be used to penetrate and guide the cannula 12 into the tissuestructure 94. Once the distal end 22 of the cannula 12 is properlypositioned, the stylet may be removed, and the array of electrodes 14may be introduced into the lumen 24 of the cannula 12.

The array of electrodes 14 may be advanced from the distal end 22 of thecannula 12 and into the tissue structure 94. Preferably, the needles 30have sufficient column strength to pass through the tissue withoutbuckling or deflecting in an unpredictable manner. The sharpened distaltips 32 may expand automatically due to the inherent bias of the needles30 to adopt the expanded configuration, such as that shown in FIG. 5B.The deployment of the array of electrodes 14 may also be monitored usingexternal imaging to ensure that the needles 30 expand as desired withinthe target region 92.

With the array of electrodes 14 deployed within the target region 92,saline (or other conductive fluid) may be introduced into the targetregion 92 via the outlets 36 communicating with the infusion lumens 34(not shown in FIG. 5B). Saline may be delivered in a single bolus,continuously, or intermittently during the treatment. The amount ofsaline introduced may be adjusted to maximize heat transfer, whileminimizing adverse effects that may result from excessive volumes ofsaline, such as cooling of the electrodes and/or excessive salinedelivery into the patient's body, as will be appreciated by thoseskilled in the art.

The RF generator 16 (not shown in FIG. 5B) may then be activated,thereby delivering RF energy to the distal portions 33 of the needles30, and, consequently, to the surrounding tissue in the target region92. Due to the presence of the saline, the amount of heat transferred tothe target region 92 may be substantially enhanced, causing a largerregion of tissue to be heated and necrosed as compared to a similarpower level of RF energy without saline. This is because the saline mayprovide a larger supply of electrons than the tissue alone (without thesaline), thereby substantially increasing the electrical conductivity ofthe tissue and allowing the RF energy to flow deeper into the tissue.

If the RF generator 16 is operated in a monopolar mode, a passiveelectrode (not shown) may be coupled to the patient, e.g., to a regionof the patient's skin (not shown). Preferably, the passive electrode hasa sufficiently large contact area such that the tissue contacted by thepassive electrode is not heated excessively. Alternatively, the RFgenerator 16 may be operated in a bipolar mode such that a heated regionis created between the electrodes, as explained in the referencesincorporated by reference above.

If the array of electrodes 14 includes needles 30 having differentlengths and curvatures, as shown in FIGS. 4 and 5B, the distal tips 32may extend different axial and radial distances into the tissue withinthe target region 92. Consequently, the array of electrodes 14 mayexpand into a generally spherical or other three-dimensional shape thatmay substantially occupy the target region 92. When saline is introducedvia the needles 30, the saline may be injected more extensively and/oruniformly through the target region 92, e.g., within a largerthree-dimensional volume. Thus, when RF energy is delivered into thetarget region 92, the increased perfusion of saline may enhance heatingof the tissue within the target region 92. This may result in a largerand more uniform three-dimensional volume being necrosed by the array ofelectrodes 14, and/or may reduce the RF delivery time necessary toablate tissue within the target region 92.

Turning to FIGS. 6A-6C, another preferred embodiment of an apparatus 110is shown that includes a cannula 112 and a pair of jaw-like electrodesor opposing members 114 extendable from the cannula 112. In addition,the apparatus 110 may include a source of electrical energy and/or asource of conductive fluid (not shown) that may be coupled to the pairof electrodes 114, similar to the embodiment described above.

The cannula 112 generally includes a proximal end 120, a distal end 122,and a lumen 124 extending between the proximal and distal ends 120, 122,thereby defining a longitudinal axis 121. The cannula 112 may be asubstantially rigid tubular member including a sharpened distal tip 128,similar to the embodiment described above. Alternatively, a flexibletubular member, such as a catheter (not shown), may be provided insteadof the cannula 112 that includes a substantially blunt or rounded distaltip (also not shown). In this alternative, the distal end of thecatheter may have a size and/or shape to facilitate substantiallyatraumatically advancing the apparatus through a body lumen or otherpassage (not shown).

The pair of electrodes 114 include first and second elongate members or“jaws” 130 including proximal and distal ends 131, 132 and defininginner surfaces 134 that are oriented generally towards one another. Thejaws 130 may be pivotally connected to one another at their proximalends 131 such that the distal ends 132 may be movable away from andtowards one another. Preferably, the jaws 130 are resilientlycompressible towards one another to define a collapsed configuration, asshown in FIG. 6A, but are biased to move away from one another towardsan expanded configuration, as shown in FIG. 6C. The jaws 130 may bebiased to assume an arcuate shape, e.g., as shown in FIG. 6C, although,alternatively, the jaws 130 may be biased to a substantially straightshape (not shown), e.g., such that the pair of electrodes 114 130 definea “V” shape in the expanded configuration.

At least one, and preferably each, of the jaws 130 includes a pluralityof hollow needles 136 extending from the inner surfaces 134, i.e.,towards the opposing jaw 130. The needles 136 include sharpened ortissue-penetrating tips 138, e.g., beveled or pointed tips, that includeoutlets 140 communicating with a lumen 142 within the respective jaw130. The lumen 142 may extend proximally from the distal-most needle 136of the respective jaw 130 to the proximal end 131. Optionally, thedistal end(s) 132 of the jaw(s) may include a sharpened tip and/or mayinclude an outlet (not shown) communicating with the lumen 142.Alternatively, the distal end(s) 132 may be blunt or rounded (not shown)to prevent the distal end(s) 132 from penetrating tissue, as explainedfurther below.

In addition, one or both jaws 130 include one or more electrodes fordelivering electrical energy to tissue engaged between the jaws 130. Forexample, the jaws 130 may be formed from electrically conductivematerial, e.g., stainless steel or Nitinol, such that the entire exposedsurface of the jaws 130 defines an electrode. Alternatively, the jaws130 may be formed from electrically insulating material, e.g., plastic,and the needles 136 and/or the inner surface(s) 134 of the jaw(s) 130may be formed from conductive material or may be coated with aconductive material. In this alternative, conductors, e.g., wires orconductive deposits (not shown), may be-provided on or in the jaws 130for delivering electrical energy to the needles 136 and/or the innersurface(s) 134. The conductors may be provided in separate lumens (notshown) within the jaws 130 or may be deposited to a surface of the jaws130 and covered with an insulating material.

The pair of electrodes 114 may be provided on a distal end 144 of anelongate member, e.g., a tubular member 146, including an infusion lumen148 communicating with the lumens 142 in each of the jaws 130.Preferably, the tubular member 146 has sufficient column strength toprovide a control element for moving, i.e., pushing and pulling, thepair of electrodes 114 axially with respect to the cannula 112. Forexample, the tubular member 146 may extend into the lumen 124 of thecannula 112 such that the tubular member 146 is slidable axiallyrelative to the cannula 112.

A proximal end (not shown) of the tubular member 146 may be coupled toan actuator and/or handle on the proximal end (also not shown) of thecannula 112. Thus, movement of the actuator or handle may direct thetubular member 146 axially within the lumen 124. Preferably, axialmovement of the tubular member 146 is used to deploy the pair ofelectrodes 114 from within the lumen 124 and/or to withdraw the pair ofelectrodes 114 into the lumen 124. For example, the tubular member 146may be pulled proximally such that the jaws 130 are resilientlycompressed towards one another as they are with drawn into the lumen 124of the cannula, as shown in FIG. .6A. When the tubular member 146 ispushed distally, as shown in FIGS. 6B and 6C, the jaws 130 mayautomatically return towards the expanded configuration.

The jaws 130 may be formed from an elastic or superelastic material,similar to the previous embodiment, that may facilitate expansion and/orresilient compression of the jaws 130. Alternatively, the jaws 130 maybe mechanically steerable such that the jaws 130 may be selectivelydirected away from one another towards the expanded configuration. Thepair of electrodes 114 may be formed as a single piece or may bemultiple pieces, e.g., separate jaws 130 that may be attached to oneanother. The pair of electrodes 114 may be connected to the distal end144 of the tubular member 146, e.g., such that the tubular member 146and the pair of electrodes 114 are substantially permanently attached toone another. Alternatively, the pair of electrodes 114 and the tubularmember 146 may be formed as a single part. In any of these embodiments,conventional manufacturing and assembly methods may be used, as will beappreciated by those skilled in the art.

Similar to the previous embodiment, a source of saline or otherconductive fluid (not shown) may be connected to the proximal end of thetubular member 146 such that saline may be delivered via the infusionlumen 148 into the lumens 142 of the jaws 130 and through the outlets140 in the needles 136. In addition, a source of electrical energy,e.g., an RF generator (not shown), may be coupled to the pair ofelectrodes 114, e.g., by a cable connected to the proximal end (also notshown) of the cannula 112 and/or the tubular member 146.

Turning to FIGS. 7A-7D, the apparatus 110 may be used to heat and/orablate tissue within a patient, similar to the previous embodiment. Theapparatus 110 may be particularly useful for ablating a tumor or othertissue at or near a surface of an organ or other soft tissue structure,such as a liver, kidney, pancreas, stomach, spleen, lung, prostate,breast, and the like. Initially, the pair of electrodes 114 may beprovided in the collapsed configuration, e.g., within the lumen 124 ofthe cannula 112 as shown in FIG. 6A.

With particular reference to FIG. 7A, with the pair of electrodes 114collapsed, the distal end 122 of the cannula 112 may be introduced intoa space 96 adjacent a tissue structure 94 within a patient that is to betreated. If the cannula 112 is substantially rigid and includes asharpened distal tip 128, the cannula 112 may inserted directly into thepatient's skin or an outer surface of an organ, through any interveningtissue, and into the space 96. Alternatively, the cannula 112 may beadvanced through tissue using an internal stylet (not shown), similar tothe embodiment described above. The stylet may be removed and then thepair of electrodes 114 may be advanced through the lumen 124 of thecannula 112 to the distal end 122.

In a further alternative, a flexible outer tubular member instead of arigid cannula 112 may be used. The distal end 122 of the outer tubularmember may be advanced along a natural body passage (not shown) into thespace 96. For example, the distal end 122 may be advanced over aguidewire or other rail (not shown) already positioned within the space96 using known methods.

Turning to FIG. 7B, the pair of electrodes 114 may be deployed from thecannula 112, and the jaws 130 may be directed away from one another tothe expanded configuration. For example, the distal end 122 of thecannula 112 may be retracted relative to the pair of electrodes 114, orthe pair of electrodes 114 may be advanced distally relative to thecannula 112. Preferably, the jaws 130 are biased to move away from oneanother automatically upon deployment from the distal end 122 of thecannula 112, although alternatively, the jaws 130 may be mechanicallyexpanded away from one another, as explained above.

As shown in FIG. 7C, the pair of electrodes 114 may be manipulated,e.g., advanced until the tissue structure 94 is disposed between thejaws 130. The jaws 130 may then be directed towards one another toengage the tissue structure 94 between inner surfaces 134 of the jaws130, as shown in FIG. 7D. Preferably, the jaws 130 are forced togetherby advancing the distal end 122 of the cannula 112 distally towards thetissue structure 94 such that the jaws 130 begin to enter the lumen 124.As the proximal ends of the jaws 130 are directed towards one another,the bias of the jaws 130 may be overcome, forcing the distal ends 132 ofthe jaws 130 towards one another. Because of the sharpened tips 138 ofthe needles 136, this action may cause the needles 136 to penetrate andenter at least partially into the tumor 92 in the tissue structure 94.

Saline or other conductive fluid may be injected from a source (notshown) via the needles 130 into the tissue structure 94. The saline maybe injected in a single bolus, intermittently, or continuously duringthe procedure, similar to the previous embodiment. The RF generator (notshown) may be coupled to the pair of electrodes 114, and RF electricalenergy may be delivered via the needles 130 and or the inner surface(s)of the jaws 130 into the tissue structure 94 to ablate all or a portionof the tissue structure 94.

Once sufficient RF energy ifs delivered, the pair of electrodes 114 maybe expanded, e.g., by partially withdrawing the cannula 112 (similar tothat shown in FIG. 7C). If desired, the pair of electrodes 114 may bemanipulated to another portion of the tissue structure 94 (not shown),and the procedure repeated to ablate additional tissue within the tissuestructure 94. Finally, the pair of electrodes 114 may be withdrawn awayfrom the tissue structure 94 and/or withdrawn into the cannula 112, andthe cannula 112 may be removed from the patient.

In embodiments of the invention, the needles are generally elongate rodsor tubes formed from an electrically conductive and porous material,e.g., sintered stainless steel, thereby providing an electrode throughwhich electrolytic fluid may flow for delivering electrical energy totissue surrounding the needle. The needles may be rigid or flexible,and/or may be straight or biased to a curved shape. A range from asingle needle to an array of needles deployable into an expandedthree-dimensional configuration, such as the configuration shown inFIGS. 1-4 and described above, may be employed.

In selected embodiments, the needles may be formed as an extruded orcast sintered rod. A beveled or sharpened distal tip may be ground orotherwise formed. Thus, the entire needle may be porous such that fluidintroduced into the proximal end of the needle may flow through thepores and exit an exposed distal portion of the needle. Additionally oralternatively, the needles may be a co-extruded sintered tube, includingan infusion lumen for delivering a fluid to an outlet in its distal tip.Thus, some of the fluid passing through the lumen may weep through thepores of the needle and exit the needle, while the remaining fluid mayexit the outlet. In a further alternative, a lumen may extend partiallyinto the needle from the proximal end, but not completely to is distaltip.

An advantage of using a sintered/porous material to form the needle(s)is that visibility of the distal portion of the needle(s) under certainimaging modalities may be enhanced. For example, the sintered/porousmaterial may substantially increase the echogenicity of the needle whenusing ultrasound imaging. Thus, the distal portion may be monitored toensure that a desired length of the needle is advanced from theintroducer sleeve into the target tissue structure. If a plurality ofneedles are provided, each of the needles may be formed fromsintered/porous material, thereby facilitating monitoring deployment ofthe array within the tissue structure.

Once the needle(s) are deployed, saline or other conductive fluid may beinjected from a source via the needle into the tissue structure. Thesaline may be injected in a single bolus, intermittently, orcontinuously during the procedure, as described herein. Because of theporous nature of the sintered material, the saline may more uniformlypermeate the surrounding tissue as compared with a needle including alumen having only one or more discrete outlets. Once sufficient RFenergy is delivered, the needle(s) are at least partially withdrawn intothe introducer sleeve, and the sleeve is removed from the patient and/ormoved to another location to ablate additional tissue.

While the invention is susceptible to various modifications, andalternative forms, specific examples thereof have been shown in thedrawings and are herein described in detail. The invention is notlimited to the particular embodiments or methods disclosed, but is toinclude all modifications, equivalents and alternatives falling withinthe scope of the appended claims.

1. An apparatus for delivering electrical energy to tissue within apatient, comprising: a tubular member comprising a proximal end, adistal end having a size for insertion into a body of a patient, and alumen extending from the distal end towards the proximal end; and aneedle comprising a distal portion extending at least partially from thelumen and terminating in a tissue-piercing distal tip, the distalportion comprising an electrically conductive and porous material,thereby providing an electrode through which electrolytic fluid may flowfor delivering electrical energy to tissue surrounding the distalportion.
 2. The apparatus of claim 1, wherein the distal portioncomprises sintered stainless steel.
 3. The apparatus of claim 1, whereinthe needle comprises a needle lumen extending from a proximal end of theneedle to the distal portion.
 4. The apparatus of claim 3, furthercomprising a source of electrolytic fluid coupled to the needle lumenfor delivering electrolytic fluid to the distal portion of the needle.5. The apparatus of claim 1, wherein the entire needle comprises porousmaterial.
 6. The apparatus of claim 1, wherein the needle is movablerelative to the tubular member for at least one of retracting the distalportion into the tubular member and deploying the distal portion fromthe tubular member.
 7. The apparatus of claim 1, wherein the tubularmember comprises an electrically insulating sleeve.
 8. The apparatus ofclaim 1, further comprising a plurality of needles extendable from thelumen beyond the distal end of the tubular member, each needlecomprising a distal tip for penetrating tissue.
 9. The apparatus ofclaim 8, wherein each of the plurality of needles comprises a distalportion comprising an electrically conductive and porous material,thereby providing an array of porous electrodes through whichelectrolytic fluid may flow for delivering electrical energy to tissueadjacent the distal portions of the array of electrodes.
 10. Anapparatus for delivering electrical energy to tissue within a patient,comprising: a tubular member comprising a proximal end, a distal endhaving a size for insertion into a body of a patient, and a lumenextending from the-distal end towards the proximal end of the tubularmember; and an array of needles extendable from the lumen beyond thedistal end of the tubular member, each needle comprising a distal tipfor penetrating tissue, at least one needle comprising a distal portioncomprising an electrically conductive and porous material, therebyproviding a porous electrode through which electrolytic fluid may flowfor delivering electrical energy to tissue adjacent the distal portion.11. The apparatus of claim 10, wherein the needles are movable from aretracted configuration within the lumen to an extended configurationwherein distal portions of the needles extend beyond the distal end ofthe tubular member.
 12. The apparatus of claim 11, wherein a pluralityof the needles have distal tips that extend different axial and radialdistances from one another in the extended configuration.
 13. Theapparatus of claim 11, wherein a distal portion of a plurality of theneedles comprises an electrically conductive and porous materialdefining an electrode.
 14. The apparatus of claim 10, further comprisinga source of conductive fluid connected to the infusion lumen of eachneedle comprising an infusion lumen.
 15. The apparatus of claim 14,further comprising a hub proximal to the distal end of the tubularmember, the hub comprising a port connected to the source of conductivefluid, the hub communicating with each infusion lumen for deliveringconductive fluid from the source of conductive fluid to each porouselectrode.
 16. The apparatus of claim 14, further comprising a floatvalve connected to the source of conductive fluid for removing gasesfrom conductive fluid being delivered from the source of conductivefluid to each porous electrode.
 17. An apparatus for deliveringelectrical energy to tissue within a patient, comprising: a tubularmember comprising a proximal end, a distal end having a size forinsertion into a body of a patient, and a lumen extending between theproximal and distal ends of the tubular member; a pair of opposingmembers extendable from the distal end of the tubular member, theopposing members being expandable away from one another and beingdirectable towards one another for engaging tissue between innersurfaces of the opposing members, the opposing members comprising one ormore electrodes for delivering electrical energy to tissue engagedbetween the opposing members; and one or more hollow needles extendingfrom an inner surface of at least one opposing member, each needlecomprising a sharpened tip for penetrating tissue engaged between theopposing members and an outlet in the sharpened tip communicating with alumen in the opposing member for delivering conductive fluid from thelumen into tissue penetrated by the sharpened tip.
 18. The apparatus ofclaim 17, wherein the opposing members extend from a control memberextending through the lumen of the tubular member, and wherein theopposing members are directable towards one another by directing thecontrol member proximally to at least partially withdraw the opposingmembers into the lumen.
 19. The apparatus of claim 18, wherein thecontrol member comprises an infusion lumen therein communicating withthe outlet of the needle via the lumen in the opposing member
 20. Theapparatus of claim 19, further comprising a source of conductive fluidcommunicating with the infusion lumen for delivering conductive fluid tothe outlet of the needle.
 21. The apparatus of claim 20, furthercomprising a float valve connected to the source of conductive fluid forremoving gases from conductive fluid being delivered from the source ofconductive fluid to the outlet of the needle.
 22. The apparatus of claim17, wherein the inner surfaces of the opposing members compriseelectrically conductive material defining the electrodes.
 23. Theapparatus of claim 17, wherein the one or more electrodes comprises oneor more electrodes coupled to a first terminal of a source of electricalenergy and one or more electrodes coupled to a second terminal of thesource of electrical energy such that the apparatus is operated in abipolar mode.
 24. The apparatus of claim 17, wherein the tubular membercomprises a substantially rigid cannula, and wherein the distal endcomprises a sharpened distal tip for penetrating tissue.
 25. Theapparatus of claim 17, further comprising a substantially rigid cannulaincluding a sharpened distal tip for penetrating tissue, and wherein thetubular member is insertable through the cannula when the opposingmembers are withdrawn into the tubular member.